The present invention relates to a method for weaving a fabric with areas having a corded structure, a backing fabric being woven on a weaving machine by inserting backing weft yarns during weft insertion cycles between binding and tension warp yarns and by inserting pattern-weft yarns outside the backing fabric, where pile warp yarns are covering the pattern-weft yarns forming cords.
This invention likewise relates to fabrics presenting areas with a corded structure, and more particularly to fabrics the areas of which are approaching a loop pile fabric or bouclé fabric and usually referred to as “false bouclé”.
Furthermore, this invention relates to a three rapierweaving machine and a rapier weaving machine with four weft insertion means which are provided for weaving fabrics in accordance with the present invention.
From the European Patent Publication EP 974690, the method is known to weave false bouclé fabrics making use of face-to-face weaving techniques, two corded fabrics being obtained presenting a loop aspect by alternately inserting a weft into the backing fabric in each fabric and subsequently two wefts, one of which is interlaced in the backing fabric, the second weft lying on top of the backing fabric, the pile warp yarns being interlaced around this weft and consequently forming a loop fitting tightly around the weft outside the backing fabric. Because of this being fitting tightly around a weft and of the absence of a cavity, because of which the loop is compressible only in a very limited way, such a loop is called a false loop or a “false bouclé”. The market shows a great interest in such fabrics, but they have the disadvantage that the colour effects which may be realised within such fabrics have their limitations, because:                the pile forming the false loop is fitting to the weft outside the backing fabric. In order to avoid, as much as possible the effect of the weft from showing through the pile loops, thicker yarns are used to that purpose. In the face-to-face weaving technique, in order to maintain the choice of colours in each area of the fabric on a maximal level, a pile warp yarn should be provided for each colour desired in every pile warp system (which normally means in every reed dent), the pile warp yarn having the colour desired, in each point of the fabric, being placed around the weft and the other pile warp yarns being hidden as dead pile in the backing fabric. The need to use a thick pile warp yarn so that the weft will be well covered, means that the number of pile warp yarns that may be used per reed dent or per warp system is limited because of the space available;        false bouclé woven face-to-face has an additional disadvantage compared to fabrics with a cut pile as far as the number of colour effects is concerned. Where with face-to-face weaving of fabrics having a cut pile, the pile-forming warp yarns are alternately interlaced around wefts of both backing fabrics, and therefore the pile is drawn between the two fabrics, a pile-forming pile warp yarn in a false bouclé fabric is interlaced around the wefts in one single fabric only, so that each pile warp yarn has to be present twice in the same reed dent, once for the upper fabric and once for the lower fabric. That is why there are twice as many pile warp yarns per reed dent for the same number of colour effects when weaving the false bouclé compared to the face-to-face weaving of fabrics with a cut pile, or in other words, the capacity of different colours per reed dent is only about half the capacity when weaving false bouclé, compared to face-to-face pile fabrics with a cut pile in case yarns having the same thickness are considered.        
Because of this, in most cases, weaving false bouclé is limited to the use of two to three colours per fabric.
It is possible to extend the palette of colours used for the fabric by applying so-called “lathing”; here each warp yarn system (a warp yarn system normally corresponding to the warp yarns in one reed dent) is using the same number of colours (for instance, two or three), however, different colours are used in different warp yarn systems. However, this technique has serious limitations, as designing is regarded.
Changing the distribution of colours among the various warp yarn systems is very time-consuming, because changes have to be carried out in the weaving creel among a large number of bobbins, consequently causing a great risk of making errors, because it is not simple to identify the right bobbin for the right warp yarn system.
In order to realize additional colour effects, it is known from various applications to use weft yarns having different colours.
With flat fabrics it is known, to use a colour selector on a weft exchanger to change the colour and/or the nature of the yarns during successive wefts, in order to obtain additional colour effects in the fabric in this manner.
Here, in those places where the effect of the weft yarn selected should be visible, the weft will be positioned above the warp yarns (seen from the useful face of the fabric). In those places where the effect of a weft yarn should be visualized, this warp yarn will be positioned at the top and the weft yarn will be positioned between the warp yarns or below the warp yarns.
Such fabrics will not offer a solution in case of pile fabrics, because with such fabrics the weft yarns are interlaced by backing warp yarns, in order to form a backing fabric. The function of the backing fabric is to constitute a solid base in which the pile warp yarns may be interlaced tightly and anchored. To put weft yarns systematically on top of the backing fabric might lead to a backing fabric no longer offering any sufficient solidity and be lacking a tight structure for interlacing the pile warp yarns tightly, because of which it would consequently be impossible to guarantee a good pile withdrawal force.
Most of the time, the backing fabric will also comprise tension warp yarns in order to be able to position the wefts inserted in various layers in order to enable higher density of the pile fabric to be obtained and also, as is the case when weaving a false bouclé, to assist to obtain a more distinct cord formation. Bringing weft from the inside of the backing fabric to the outside might likewise disturb this subdivision of the wefts into several layers and therefore endanger the quality of the fabric.
The German publication of the patent DE 19924214 describes a special Jacquard machine for weaving pile fabrics with a large palette of colours by alternating the areas with a cut pile with areas having no pile at all in which colourful effects are realized by means of different weft yarns. By means of this the so-called Italian Jacquard fabrics are woven in which not only the pile warp yarns, but also the backing warp yarns will be activated by a Jacquard machine, and in doing so, allowing to modify the position of the backing warp yarns in areas where there is no pile and this, not only within one warp yarn system but also over different warp yarn systems in order to be able to solve the said problems and to be able to apply the effects of the weft used for weaving flat fabrics also to pile fabrics.
The solution to activate the backing warp yarns by means of a Jacquard machine will cause the investment to be an expensive one and will make the method used and the backing fabric to become complicated.
Furthermore, for weaving false bouclé, it is customary, already for a longer period, to use a coloured yarn or a yarn with a special effect as a weft yarn lying on top of the backing fabric and to prevent this weft yarn in certain places from being interlaced by a pile warp yarn. This will provide an additional possibility for a variety of colour with respect to the use of pile warp yarns only, but it has the great disadvantage that it is only possible to add one additional colour or effect which, moreover, is the same colour or effect each time across the width of the weaving machine (in the weft direction).